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Application of the Galileo system for a better synchronization of electrical power systems ; Capitanescu, Florin ; et al (2007, July) In this paper we present objectives and strategies of the NAVELEC research project funded by the European Union Galileo Joint Undertaking (GJU/05/2423). The project objective is to assess how the European ... [more ▼] In this paper we present objectives and strategies of the NAVELEC research project funded by the European Union Galileo Joint Undertaking (GJU/05/2423). The project objective is to assess how the European Global Navigation Satellite System related solutions can enhance the operation and control of the European power system over wide areas. Some basic functionalities of the GALILEO system are given first, then we summarize the questionnaire, set at the initial stage of the project, and provide the analysis of received responses from transmission system operators. Two generic strategies to upgrade existing electrical power transmission networks with functionalities, as well as major steps to upgrade underlying infrastructures, are discussed in this paper. [less ▲] Detailed reference viewed: 33 (1 ULg)Improving the statement of the corrective security-constrained optimal power flow problem Capitanescu, Florin ; Wehenkel, Louis in IEEE Transactions on Power Systems (2007), 22(2), 887-889 This letter proposes a formulation of the corrective security-constrained optimal power-flow problem imposing, in addition to the classical post-contingency constraints, existence and viability ... [more ▼] This letter proposes a formulation of the corrective security-constrained optimal power-flow problem imposing, in addition to the classical post-contingency constraints, existence and viability constraints on the short-term equilibrium reached just after contingency. The rationale for doing so is discussed and supported by two examples. [less ▲] Detailed reference viewed: 52 (2 ULg)Interior-point based algorithms for the solution of optimal power flow problems Capitanescu, Florin ; ; Ernst, Damien et al in Electric Power Systems Research (2007), 77(5-6), 508-517 Interior-point method (IPM) is a very appealing approach to the optimal power flow (OPF) problem mainly due to its speed of convergence and ease of handling inequality constraints. This paper analyzes the ... [more ▼] Interior-point method (IPM) is a very appealing approach to the optimal power flow (OPF) problem mainly due to its speed of convergence and ease of handling inequality constraints. This paper analyzes the ability of three interior-point (IP) based algorithms, namely the pure primal-dual (PD), the predictor-corrector (PC) and the multiple centrality corrections (MCC), to solve various classical OPF problems: minimization of overall generation cost, minimization of active power losses, maximization of power system loadability and minimization of the amount of load curtailment. These OPF variants have been formulated using a rectangular model for the (complex) voltages. Numerical results on three test systems of 60, 118 and 300 buses are reported. (C) 2006 Elsevier B.V. All rights reserved. [less ▲] Detailed reference viewed: 71 (10 ULg)Model predictive control and reinforcement learning as two complementary frameworks Ernst, Damien ; ; Capitanescu, Florin et al in International Journal of Tomography & Statistics (2007), 6 Model predictive control (MPC) and reinforcement learning (RL) are two popular families of methods to control system dynamics. In their traditional setting, they formulate the control problem as a ... [more ▼] Model predictive control (MPC) and reinforcement learning (RL) are two popular families of methods to control system dynamics. In their traditional setting, they formulate the control problem as a discrete-time optimal control problem and compute a suboptimal control policy. We present in this paper in a unified framework these two families of methods. We run for MPC and RL algorithms simulations on a benchmark control problem taken from the power system literature and discuss the results obtained. [less ▲] Detailed reference viewed: 67 (13 ULg)Model predictive control and reinforcement learning as two complementary frameworks Ernst, Damien ; ; Capitanescu, Florin et al in Proceedings of the 13th IFAC Workshop on Control Applications of Optimisation (2006) Model predictive control (MPC) and reinforcement learning (RL) are two popular families of methods to control system dynamics. In their traditional setting, they formulate the control problem as a ... [more ▼] Model predictive control (MPC) and reinforcement learning (RL) are two popular families of methods to control system dynamics. In their traditional setting, they formulate the control problem as a discrete-time optimal control problem and compute a suboptimal control policy. We present in this paper in a unified framework these two families of methods. We run for MPC and RL algorithms simulations on a benchmark control problem taken from the power system literature and discuss the results obtained. [less ▲] Detailed reference viewed: 119 (6 ULg)Applications of security-constrained optimal power flows Capitanescu, Florin ; ; Ernst, Damien et al in In Proceedings of Modern Electric Power Systems Symposium, MEPS06 (2006) This paper proposes to formulate security control as a sequential decision making problem and presents new developments in automatic learning of sequential decision making strategies from simulations and ... [more ▼] This paper proposes to formulate security control as a sequential decision making problem and presents new developments in automatic learning of sequential decision making strategies from simulations and/or information collected from real-life system measurements. The exploitation of these methods for the design of decision making strategies and control policies in the context of preventive and emergency mode dynamic security assessment and control is discussed and further opportunities for research in this area are highlighted. [less ▲] Detailed reference viewed: 109 (0 ULg)A hybrid optimization technique coupling an evolutionary and a local search algorithm Kelner, Vincent ; Capitanescu, Florin ; Léonard, Olivier et al in Journal of Computational & Applied Mathematics (2006), 215(2), 281-287 Evolutionary algorithms are robust and powerful global optimization techniques for solving large-scale problems that have many local optima. However, they require high CPU times, and they are very poor in ... [more ▼] Evolutionary algorithms are robust and powerful global optimization techniques for solving large-scale problems that have many local optima. However, they require high CPU times, and they are very poor in terms of convergence performance. On the other hand, local search algorithms can converge in a few iterations but lack a global perspective. The combination of global and local search procedures should offer the advantages of both optimization methods while offsetting their disadvantages. This paper proposes a new hybrid optimization technique that merges a genetic algorithm with a local search strategy based on the interior point method. The efficiency of this hybrid approach is demonstrated by solving a constrained multi-objective mathematical test-case. [less ▲] Detailed reference viewed: 45 (9 ULg)Experience with the multiple centrality corrections interior point algorithm for optimal power flow Capitanescu, Florin ; ; Wehenkel, Louis in CEE 05 conference (2005, October) This paper analyzes the ability of the Multiple Centrality Corrections (MCC) interior point algorithm to solve various classical optimal power flow (OPF) variants, namely: the minimization of generation ... [more ▼] This paper analyzes the ability of the Multiple Centrality Corrections (MCC) interior point algorithm to solve various classical optimal power flow (OPF) variants, namely: the minimization of generation cost, the minimization of active power losses, the maximization of power system loadability and the minimization of the amount of load curtailment. The performances of the MCC approach are assessed with respect to the predictor-corrector algorithm, which is widely recognized as the best interior point method based optimizer to date. Illustrative examples on three test systems up to 300 buses are provided. [less ▲] Detailed reference viewed: 27 (0 ULg)Applications of an interior point method based optimal power flow Capitanescu, Florin ; ; Wehenkel, Louis in CEE 05 conference (2005, October) This paper tackles the complex problem of an Optimal Power Flow (OPF) by the Interior Point Method (IPM). Two interior point algorithms are presented and compared, namely the pure primal-dual and the ... [more ▼] This paper tackles the complex problem of an Optimal Power Flow (OPF) by the Interior Point Method (IPM). Two interior point algorithms are presented and compared, namely the pure primal-dual and the predictor-corrector respectively. Among various OPF objectives, emphasis is put on two classical ones: the maximization of power system loadability and the minimization of the amount of load curtailment. Illustrative examples on three test systems of 60, 118 and 300 buses are provided. [less ▲] Detailed reference viewed: 26 (2 ULg)An interior point method based optimal power flow Capitanescu, Florin ; ; Wehenkel, Louis (2005, June) This paper deals with the solution of an optimal power flow (OPF) problem by the interior point method (IPM). The latter is a very appealing approach to this nonlinear programming problem due to its speed ... [more ▼] This paper deals with the solution of an optimal power flow (OPF) problem by the interior point method (IPM). The latter is a very appealing approach to this nonlinear programming problem due to its speed of convergence and ease of handling inequality constraints. Two interior point algorithms are presented and compared: the pure primal-dual and the predictor-corrector. Several implementation aspects of these IPM algorithms are also discussed. The OPF is formulated in rectangular coordinates which confers some significant advantages because generally its objective and constraints are quadratic functions. Among the large variety of OPF objectives, emphasis is put on two classical ones: the minimization of generation cost and the minimization of transmission active power losses. The solution obtained by both algorithms proves to be robust for the two OPF sub-problems (optimization of active power flows and reactive power flows) as well as for a full OPF applied to the former objective, which is unanimously recognized as the hardest problem to solve. Finally, numerical results on three test systems ranging from 60 to 300 buses are provided. [less ▲] Detailed reference viewed: 73 (0 ULg)Unified sensitivity analysis of unstable or low voltages caused by load increases or contingencies Capitanescu, Florin ; Van Cutsem, Thierry in IEEE Transactions on Power Systems (2005), 20(1), 321-329 This paper deals with the analysis of situations where load increases and/or contingencies cause transmission voltages to become unstable or unacceptably low. Simple sensitivities are proposed to ... [more ▼] This paper deals with the analysis of situations where load increases and/or contingencies cause transmission voltages to become unstable or unacceptably low. Simple sensitivities are proposed to determine the relative efficiency of candidate remedial actions, which are parameter changes likely to strengthen the system. To this purpose, the sensitivities of the bus voltage magnitude experiencing the largest drop are considered. In the neighborhood of a loadability limit or a critical point, it is shown that these sensitivities and those based on eigenvalue and eigenvector computation are essentially the same. However, the proposed analysis can also deal with low but stable situations. The accuracy of the proposed sensitivities is demonstrated on the models of two real systems, in which the parameters of concern are bus power injections. [less ▲] Detailed reference viewed: 62 (6 ULg)Preventive assessment and enhancement of power system voltage stability: an integrated approach of thermal and voltage security Capitanescu, Florin Doctoral thesis (2003) This thesis is devoted to the preventive assessment and enhancement of voltage stability and security in electric power systems. However, in the course of deriving all the proposed methods we have paid ... [more ▼] This thesis is devoted to the preventive assessment and enhancement of voltage stability and security in electric power systems. However, in the course of deriving all the proposed methods we have paid attention to keeping them compatible with the (more traditional) handling of thermal overloads, thereby providing a unified treatment of voltage and thermal security. The approaches presented in this work apply to both deregulated environments and classical, vertically integrated ones. The heart of most methods developed in this thesis is : (i) the derivation of sensitivities indicating the relative efficiency of the various bus injections to restore voltage stability or increase an insufficient voltage security margin, and (ii) the use of these sensitivities in linearized security constraints that can be incorporated to various optimization problems. Using this formulation, we deal with three different problems of interest in preventive security analysis: 1) Congestion management. We propose two optimization-based approaches to manage congestions due to voltage instability and/or thermal overload. The control variables are either power injections (generation rescheduling and load curtailment) or power transactions; 2) Computation of Available Transfer Capabilities (ATCs). We determine the simultaneous ATCs of multiple transactions by means of a single optimization-based computation; 3) evaluation of security margins interval. To face the uncertainty affecting power transfers, we present an optimization-based computation of the minimal and maximal margins under the assumption that individual injections vary within specified bounds. Besides this main theme, the thesis offers additional reflections on the: 1) Filtering of contingencies. We propose a simple and reliable technique to filter out harmless contingencies when computing voltage security margins of a large set of contingencies; 2) Evaluation of reactive reserves with respect to a contingency, an important topic for voltage security reasons as well as within the context of a deregulated market where providing reactive reserves is an ancillary service which should be properly paid. Most of the methods proposed in this thesis were successfully tested on realistic power system models. From a practical viewpoint all the above computations have been coupled to the fast time-domain quasi steady-state simulation used in the ASTRE software developed at the University of Liège. [less ▲] Detailed reference viewed: 103 (10 ULg)Computation of simultaneous available transfer capability under thermal and voltage security constraints Capitanescu, Florin ; Van Cutsem, Thierry (2002, September) This paper proposes a method to compute the Available Transfer Capability (ATC) of a power system under both thermal and voltage security constraints. The objective is to determine, in some optimal manner ... [more ▼] This paper proposes a method to compute the Available Transfer Capability (ATC) of a power system under both thermal and voltage security constraints. The objective is to determine, in some optimal manner, the ATC of several simultaneous transactions, such that any postulated contingency does not cause voltage instability nor thermal overloads. Thermal constraints are derived for every branch likely to be overloaded in post-contingency states. Voltage security constraints are derived from voltage unstable post-contingency scenario, obtained by Quasi Steady- State simulation, a fast time-domain method. The paper also addresses the discrimination problem, i.e. the fact that the computed ATC might favor some trades to the detriment of others. Variants will be discussed to deal with such situations. The method is illustrated on an 80-bus test system. [less ▲] Detailed reference viewed: 55 (6 ULg)Evaluating bounds on voltage and thermal security margins under power transfer uncertainty Capitanescu, Florin ; Van Cutsem, Thierry (2002, June) This paper deals with the evaluation of bounds on voltage and thermal security margins with respect to contingencies. A margin is the maximual pre-contingency power transfer between either a generation ... [more ▼] This paper deals with the evaluation of bounds on voltage and thermal security margins with respect to contingencies. A margin is the maximual pre-contingency power transfer between either a generation and a load area or two generation areas, such that the specified contingencies do not overload lines or make the system voltage unstable. The minimum and maximum margins are computed for given intervals of variations of bus injections. Each bound is the solution of a constrained L1-norm minimization (or maximization) problem, for which specific algorithms are given. Thermal overloads are handled through linearization, while for voltage stability, fast time simulation and instability mode analysis are used. Nonlinear situations of branch overloads are also considered. The method is illustrated on an 80-bus test system. [less ▲] Detailed reference viewed: 64 (11 ULg)Preventive control of voltage security margins: A multicontingency sensitivity-based approach Capitanescu, Florin ; Van Cutsem, Thierry in IEEE Transactions on Power Systems (2002), 17(2), 358-364 This paper addresses the problem of changing the operating point of a power system in order to keep voltage security margins with respect to contingencies above some minimal value. Margins take on the ... [more ▼] This paper addresses the problem of changing the operating point of a power system in order to keep voltage security margins with respect to contingencies above some minimal value. Margins take on the form of maximum pre-contingency power transfers either between a generation and a load area or between two generation areas. They are determined by means of a fast time-domain method. We will first discuss the use of a general optimal power flow, in which linear voltage security constraints are added. The simultaneous control of several (possibly conflicting) contingencies is considered. Then, we will focus on the minimal control change objective. Among the possible controls, emphasis is put on generation rescheduling and load curtailment. Examples are presented on an 80-bus test system as well as on a real system. [less ▲] Detailed reference viewed: 87 (13 ULg)Evaluation of reactive power reserves with respect to contingencies Capitanescu, Florin ; Van Cutsem, Thierry (2001, August) Detailed reference viewed: 100 (5 ULg)An advanced tool for Preventive Voltage Security Assessment Van Cutsem, Thierry ; Capitanescu, Florin ; et al (2000, May) This paper deals with methods for the preventive assessment of voltage security with respect to contingencies. We describe a computing tool for the determination of secure operation limits, together with ... [more ▼] This paper deals with methods for the preventive assessment of voltage security with respect to contingencies. We describe a computing tool for the determination of secure operation limits, together with methods for contingency filtering. Examples from two very different real-life systems are provided. We outline extensions in the field of preventive control. [less ▲] Detailed reference viewed: 103 (7 ULg) |
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